Pencil eraser

The Pencil eraser (originally called a "rubber") is an item which is now considered common. They are on the end of almost every American pencil, and can also be bought separately for very cheap prices. They are made from sticky or abrasive substance (or both) to remove graphite and other marks made by powder.

History

The idea of removing mistakes or other unneeded text from writing is nothing new. In the time of the Roman Empire, wax tablet were used for writing on, and palimpsests were used to remove unwanted text. When Pencils were invented, they proved to be useful items even without erasers. However, sometimes a way to remove writing still was needed. It was eventually found that white bread could be used for this purpose, so this became the accepted practice until the 1770s when better erasure was needed.
In 1770, Joseph Priestley described rubber as "a substance excellently adapted to the purpose of wiping from paper the mark of black lead pencil." However, his idea did not catch on. Rather, a British engineer named Edward Nairne was credited with the discovery of rubber as an eraser that same year. He claimed that he had inadvertently used rubber instead of bread crumbs when attempting to erase pencil marks. Nairne is credited with developing Europe's and first rubber eraser, though some still question whether he actually came upon this idea by accident.
Rubber erasers were an interesting creation, but there is still a problem. Like bread, rubber spoils over time. However, in 1839, Charles Goodyear invented a process by which rubber could be vulcanized, which prevented it from spoiling. Only then did rubber become a common substance for a variety of applications. Among other uses, vulcanized rubber became the standard component of pencil erasers. This more than anything else made rubber erasers commonplace. Then in 1858, a Philadelphian man named Hymen Lipman patented the idea of putting erasers on the end of pencils. He attached small pieces of eraser (called plugs to this day) to the back end of the pencil with ferrules. This patent was later overturned, but the idea quickly caught on in America. However, most European pencils still do not include erasers.

Varieties

Erasers have continues to develop and change. Erasers made solely from vulcanized rubber have become less popular, while other types have arisen. The most popular kind of modern eraser which us usually a pink color and coarse to the touch is made with pulverized pumice (volcanic ash), such as the popular Pink Pearl brand.

A Vinyl block eraser

Another common variety is the relatively new vinyl eraser. Tpolyvinyl chloride, mixed with calcium carbonate (which neutralizes hydrogen chloride, produced as PVC ages), and Pthlalate plasticizers (which keeps the material soft) is used to create this effective and minimally abrasive eraser.
Other varieties have also been created, including art gum erasers (which do not damage paper, but leave significant residue) and kneaded erasers (which leave no residue and do not wear away).

How they work

The graphite in modern pencils slowly designates when rubbed against a course surface. When used on paper as intended, the graphite particles will mingle with the paper fiber, and stick there. To remove these marks, it must be pulled away by a sticker substance, or scraped away with something abrasive. Rubber erasers remove primarily by pulling, though also somewhat by scraping. Pumice erases are more abrasive, and vinyl is more "sticky," though both have the opposite property as well. Gum and Kneaded erasers work entirely by pulling the graphite out of the paper fiber without damaging the paper itself. For this reason, these two are often preferred by artists. However, Pumice and Vinyl erasers are still used most commonly, since minor paper damage is usually of no concern and these are more convenient to work with.

Notes

• Although erasers have evolved significantly, some artists still use bread to lighten charcoal or pastel marks